Lubricating oil compositions

ABSTRACT

AN ADDITIVE HAVING DETERGENCY PROPERTIES FOR INCORPORATION IN LUBRICATING OILS AND LUBRICATING OIL COMPOSITIONS CONTAINING SAD ADDITVE. THE ADDTIVE AS THE CONDENSATION PRODUCT OF AN ALIPHATIC POLYAMINE AND A MIXTURE OF A MONOCARBOXYLIC ACID AND A POLYHALO ALIPHATIC ACID HAVING A TERMINAL-CF3 GROUP IN WHICH AT LEAST 50% OF THE AMINO GROUPS OF THE POLYAMINE ARE VONVERTED TO AMIDE GROUPS BY CONDENSATION WITH THE MIXTURE OF ACIDS. THE PREFERRED LUBRICATING OIL COMPOSITION IS A 2-CYCLE ENGINE OIL COMPRISING A MAJOR PROPORTION OF A HYDROCARBON LUBRICATION OIL AND A MINOR PROPORTION OF THE ADDITIVE OF THIS INVENTION.

3,784,473 LUBRICATING OIL COMPOSITIONS Alphonso W. Marcellis, Boonton, and Paul M. Kerschner, Trenton, N.J., assignors to Cities Service Oil Company, Cranbury, NJ. No Drawing. Filed Apr. 26, 1971, Ser. No. 137,668 Int. Cl. Cm N36 US. Cl. 252--51.5 A 4 Claims ABSTRACT OF THE DISCLOSURE An additive having detergency properties for incorporation in lubricating oils and lubricating oil compositions containing sad additve. The addtive s the condensaton product of an aliphatic polyamine and a mixture of a monocarboxylic acid and a polyhalo aliphatic acid having a terminal CF group in which at least 50% of the amino groups of the polyamine are converted to amide groups by condensation with the mixture of acids. The preferred lubricating oil composition is a 2-cycle engine oil comprising a major proportion of a hydrocarbon lubricating oil and a minor proportion of the additive of this invention.

BACKGROUND OF THE INVENTION Engine lubricating oils often require the addition thereto of various additives to improve various properties. There is often a need, for example, to impart detergency properties and to enhance the lubricity of a lubricating oil composition. The need for detergency arises from the need to keep engine parts free from varnish and sludge build-up as well as the need to keep combustion products and sludge in suspension in the oil.

The foregoing is especially true in the case of 2-cycle engine operation where the lubricating oil is mixed with the fuel. The main requirement is to keep the pistons and rings free from deposits, the principal cause of which is incomplete combustion of the fuel/oil mixture to form deposit precursors. The deposit precursors then polymerize to resins which form varnish and sludge.

Another type of deposit build-up in 2-cycle engines is the accumulation of carbon deposits in the exhaust ports or the mufiier system. Such deposit build-up results in back pressure which causes power loss, particularly with smaller engines. Therefore, the residue from the combustion of the oil, which is burned with the fuel in the combustion chamber, should be in the form of a friable ash which does not build up in critical areas.

Still another type of deposit build-up is the formation of a Whisker of lead salts across the electrode gap of the spark plug. This necessitates frequent plug removal and cleaning.

The mechanism for deposit control due to the presence of a detergent, or dispersant, in the lubricating oil is postulated to be similar in 2-cycle and 4-cyc1e engines. The detergent is adsorbed on the carbonyl and carboxyl groups of the droplets of deposit precursors and resins to form a protective film which prevents these droplets from agglomerating into varnish and sludge. These detergents also keep the deposit precursors and resins suspended in the air/fuel mixture within the combustion chamber for more complete burning or to exit with the gases at the exhaust ports. In addition, the detergent present in the crankcase oil of 4-cycle engines keeps combustion products and sludge in suspension in the oil to thereby prevent sludge build-up in the cranckcase.

It is proposed that the ability of detergent additives to surround deposit precursors and resin droplets is a function of the detergents ability to plate out on the Patented Jan. 8, 1974 surface of the metal where it acts as a lubricant in its own righ, thus enhancing the lubricity of the oil composition. It is Well known that the frictional properties of oils are related to the rate of chemical and/or physical adsorption, the number of layers adsorbed, and the strength of the adsorbed films. Thus there is an apparent relationship between frictional properties of engine oils and engine cleanliness, e.g., the higher the degree of lubricity of the oil, the cleaner the engine. Therefore, the lubricity due to an additive of this invention is a function of its dispersant power. Accordingly, by measuring the lubricity of an oil composition containing a detergent additive, a measure of the additives dispersing power is obtained.

It is a desirable feature of lubricating oil additives that they be thermally stable in view of the elevated temperatures to which they are subjected. This is particularly true in the case of 2-cycle engine oils where the oil is mixed with and burned with the fuel.

SUMMARY OF THE INVENTION It is an object of this invention to provide a lubricating oil additive having detergency properties.

It is another object of this invention to provide an ashless lubricating oil additive having, in addition to detergency properties, thermal stability and lubricity characteristics as Well as rust inhibitory properties.

It is yet another object of this invention to provide a lubricating oil composition having improved detergency properties.

Still another object of this invention is to provide a lubricating oil composition having enhanced lubricity and thermal stability as well as rust inhibitory characteristics.

Other objects and advantages of this invention will be apparent to those skilled in the art from this disclosure.

The foregoing objects are achieved in accordance with this invention. In general, this invention consists of an additive for hydrocarbon lubricating oils comprising the condensation product of an aliphatic polyamine and a mixture of a monocarboxylic acid and a polyhalo aliphatic acid hving a terminal -CF group wherein at least of the amino groups of the polyamine are converted to amide groups by condensation with the mixture of acids; and a hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and a minor proportion of the additive of this invention.

Thus by practicing the instant invention, an ashless detergency additive for hydrocarbon lubricating oils is obtained. The additive has, in addition to detergency properties, thermal stability and lubricity characteristics as well as rust inhibitory properties. Hydrocarbon lubricating oil compositions containing the additive of this invention exhibit rust inhibitory properties as well as increased lubricity and thermal stability and, in addition, engines lubricated by said hydrocarbon lubricating oil compositions are characterized by enhanced cleanliness.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is concernedwith ashless detergency additives for hydrocarbon lubricating oils and hydrocarbon lubricating oil composition containing said additives. The additives of this invention impart to hydrocarbon lubricating oils superior detergency properties as well as enhanced lubricity. Hydrocarbon lubricating oil compositions of this invention are also characterized by improved thermal stability as well as enhanced rust inhibitory properties. In addition, engines lubricated with the hydrocarbon lubricating oil compositions of this invention exhibit enhanced cleanliness.

The detergency additive of this invention comprises the condensation product of an aliphatic polyamine and a mixture of a monocarboxylic acid and a polyhalo aliphatic acid having a terminal CF group wherein at least 50% of the amino groups of the polyamine are converted to amide groups by condensation with the mixture of acids.

The aliphatic polyamine contains from 2 to about 30 carbons and preferably from about 3 to about 20 carbons. The number of amino groups ranges from 2 to about 16 and preferably from 2 to about 8. While aliphatic polyamines in general are useful, polyalkylenepolyamines are preferred. Examples of suitable aliphatic polyamines are ethylenediamine; 1,3-propylenediamine; hexamethylenediamine; 1,20-diaminoeicosane; 1,8-diaminododecane; and 1,8-diaminooctane. Examples of the preferred class of polyalkylenepolyamines are diethylenetriamine, triethylenetetramine, low molecular weight polymers of ethylenediamine containing about 15 repeating units and hence about 30 carbons and about 16 amino groups, and low molecular weight polymers of ethylenediamine containing about 7 repeating units and hence about 14 carbons and about 8 amino groups. The most preferred aliphatic polyamine is tetraethylenepentamine.

The monocarboxylic acid broadly contains about 8 to 30 carbons and preferably about 12 to 24 carbons. The monocarboxylic acid may be a branched chain aliphatic acid, an aromatic acid containing a branched aliphatic chain having at least 12 carbons on the aromatic ring, or a naphthenic acid containing a branched aliphatic chain having at least 12 carbons on the naphthenic ring. The preferred class of monocarboxylic acids are the branched chain aliphatic acids containing about 8 to 30, and preferably about 12 to 24, carbons. Examples of suitable monocarboxylic acids are S-methylheptanoic acid, 9-ethyldodecanoic acid, 18-butyleicosoic acid, S-ethyldecanoic acid, p-isostearylbenzoic acid, 4 isododecyl-l-cyclohexanoic acid, 4-(17-ethyloctadecyl) 1 naphthoic acid, and 1-isododecyl-S-carboxycyclooctane. The preferred monocarboxylic acid is isostearic acid.

The polyhalo aliphatic acid contains about 4 to 24 carbons and preferably about 8 to 16 carbons and has a terminal CF group. The remainder of the molecule may or may not contain additional halogen. Aside from the fluorine in the terminal CF group, any additional halogen in the molecule may be fluorine, chlorine, bromine, iodine, or combinations thereof. The halogen content of the polyhalo aliphatic acid may range from the 3 fluorines in the terminal CF group to a perhalo acid in which all the hydrogens bonded to carbon are replaced by halogens. Perfiuoro aliphatic acids are preferred. Examples of suitable polyhalo aliphatic acids are 4,4,4-trifluorobutyric acid; 2-chloro-6,6,6-trifluorohexanoic acid; 2,2-dichloro-4,S-dibromo- 10, 10,10-trifluorodecanoic acid; 2-iodo-12,12,12-trifluorododecanoic acid;

16, 16,16-trifluorohexadecanoic acid;

perfluoroeicosoic acid;

perfluoro(Z-butyleicosoic) acid; 2,2,3,3-tetraiodo-4,4,4-trifiuorobutyric acid; 9,10-dichloro-18,18,18-trif1uorooleic acid; and perfluoro(Z-ethyldodecanoic) acid.

The preferred polyhalo aliphatic acid is perfiuorooctanoic acid.

The mixture of monocarboxylic acid and polyhalo aliphatic acid having a terminal -CF group which is condensed with the aliphatic polyamine is broadly comprised of about 50 mole percent to about 99 mole percent of the monocarboxylic acid and about 50 mole percent to about 1 mole percent of the polyhalo aliphatic acid. It is preferred, however, that the mixture of acids be comprised of about 70 mole percent to about 95 mole percent of the monocarboxylic acid and about 30 mole percent to about mole percent of the polyhalo aliphatic acid. In the case Where the mixture of acids is comprised of the preferred isostearic acid and perfiuorooctanoic acid, the mixture is preferably comprised of about mole percent of isostearic acid and about 10 mole percent of perfiuorooctanoic acid.

The ratio of the mixture of carboxylic acids to the aliphatic polyamine is such as to convert about 50% to of the amino groups of the polyamine to amide groups by condensation with the mixture of carboxylic acids. It is preferred that about 60% to 90% of the amino groups of the aliphatic polyamine be converted to amide groups. In the case where the additive is the condensation product of tetraethylenepentamine and a mixture of isostearic acid and perfluorooctanoic acid, it is especially preferred that the ratio of the mixture of acids to the tetraethylenepentamine be such as to convert about 60% of the amino groups to amide groups.

The lubricating oil compositions of our invention broadly comprise a major proportion of a hydrocarbon lubricating oil and a minor proportion of the inventive additive. Generally, the lubricating oil compositions contain about 1 to 20% by volume, based on the lubricating oil composition, of the additive of this invention. It is preferred that the lubricating oil composition contain about 2 to 10% by volume, based on the lubricating oil composition, of additive.

The additive of the instant invention is useful in hydrocarbon lubricating oils generally. However, it is contemplated that the additive will have its greatest utility in hydrocarbon engine oils, particularly in 2-cycle engine oils.

Our invention will be further illustrated by the following specific examples.

EXAMPLE I To a 500 ml. round bottom flask fitted with magnetic stirrer, thermometer, Dean-Stark trap, condenser, and nitrogen inlet tube are added 18.9 g. (0.1 mole) of tetra ethylenepentamine. The stirred amine is heated to C. while nitrogen is slowly purged through the system. To the stirred amine at 120 C. is added a mixture of 12.4 g. (0.03 mole) of perfluorooctanoic acid and 83.4 g. (0.27 mole) of Emery 871 isostearic acid over a ten minute period. The stirred reaction mixture is heated at C. for 1 hour and then at 200 C. for 1 additional hour while water of condensation is removed from the reaction mixture and collected in the Dean-Stark trap. The mixture is then stirred at C. under a pressure of 2-4 mm. Hg for an additional 12 hours to remove residual Water and any unreacted acid. The yield of product is 88.4 g., 80.5% of the theoretical yield. Infrared spectroscopy shows that the amide is formed.

As mentioned above, the effectiveness of the additives of this invention as dispersants in lubricating oil compositions is indicated by and is a function of the lubricity imparted to the oil compositions by said additives. From friction data, the Lubricity Index (LI at six different temperatures is determined. The Normal Lubricity Index (NLI) is the average of the Lubricity Indexes at the six temperatures. The Lubricity Index is determined from the expression:

wherein the lower case letters are for frictional values of a standard oil composition and the upper case letters are the corresponding frictional values for an oil composition containing the experimental additive of this invention.

a=static coefiicient of friction b=coefiicient of friction at 2 f.p.m.

b'=coefficient of friction at 50 f.p.m.

d=coefficient of slip-stick static coefficient of friction/ coeificient of friction at 2 f.p.m.

d'=ratio of coefiicient of friction at f.p.m. to coefficient of friction at 100 f.p.m. LI =Lubricity Index at T F.

The Lubricity Index is determined at 100 F., 150 F., 200 F., 250 F., 300 F., and 350 F. The Normal Lubricity Index (NLI), an average of these six Lubricity Indexes, is represented by the expression:

NLI LIIOO o LIzoo LIzso I aoo 350 From the foregoing it can be seen that if an oil composition containing an additive of this invention is equal in lubricity to the standard oil composition at a given temperature T, it will have a value for LI of 100. A value for LI less than 100 indicates poorer lubricity than the standard and a value for LI greater than 100 indicates better lubricity than the standard at temperature T. The same holds true for Normal Lubricity Index (NLI) which is an average of the Lubricity Indexes at the six different temperatures. Thus if an oil composition containing an additive of this invention has a NLI value greater than 100, it will have greater lubricity than the standard oil composition and hence it will have better dispersant power.

The friction data are obtained by using the friction apparatus and procedure described by Hain in a paper entitled Performance of Oil Additives. The paper was presented at Session 5C of a convention of the American Society of Lubrication Engineers at Chicago, 111., on May 28, 1964.

The friction apparatus is essentially a modified drill press containing a temperature recorder, a variable speed motor, and a single channel strain gauge to measure coefiicient of friction. The friction couple used in these experiments is blotter paper vs. polished, cold rolled steel. The blotter paper is chosen because of its consistent p0- rosity and surface roughness. The consistent porosity insures uniform results from day to day.

A 2-cycle engine oil composition is prepared containing 10 volume percent of the inventive additive for which the preparation is described above. For comparison, a 2-cycle engine oil composition containing 10 volume percent of a commercially available additive is prepared. The 2-cycle engine oil composition containing the additive of the invention is found to have a NLI of 122 While the 2- cycle engine oil composition containing the commercial additive has a NLI of 100.

Since, as pointed out above, an increase in the lubricity of a Z-cycle engine oil results in improved engine cleanliness, a 2-cycle engine operating on a fuel/oil mixture in which the oil contains the lubricity-improving additive of this invention will operate cleaner with less deposit buildup then it will on a similar fuel/oil mixture in which the oil contains the commercially available additive.

EXAMPLE II bBse samDl base The oil composition containing the inventive additive exhibits an 87.0% reduction in IFT while the oil composition containing the commercial additive exhibits an 85.2% reduction in IFT. There is evidence that IFT is a measure of the detergency activity of an oil and that additives which produce a large percent reduction in IFT also exhibit detergency properties.

:| 100=Percent reduction in IFT 6 EXAMPLE 111 The lubricating oil compositions of Example II containg 10 volume percent of the inventive additive of Example I and 10 volume percent of the commercially available additive, as well as the base hydrocarbon oil containing no additive, are subjected to the ASTM D665A rust test. The steel test pieces from the oil composition containing the inventive additive and from the oil composition containing the commercial additive have no rust. In contrast, the steel test piece from the base oil is severely rusted. This illustrates that the additive of this invention is as effective as the commercially available additive in imparting rust inhibitory properties to hydrocarbon lubricating oils.

EXAMPLE IV The lubricating oil compositions of Example II containing 10 volume percent of the inventive additive of Example I and 10 volume percent of the commercially available additive, as well as the base hydrocarbon oil containing no additive, are subjected to the Shell Four Ball Wear test. The test involves placing three stationary steel balls in triangular configuration in a cup containing the oil composition to be tested while a fourth ball which is rotatable and capable of having a load applied thereto is brought into contact with the three stationary balls in such a way as to form a four ball pyramid. The conditions of the test are to rotate the fourth ball at 1800 rpm. at a temperature of F. for one hour. The test is run under loads of 7.5 kg. and 40 kg. At the end of the test, the wear, i.e., the average of the scar diameters of the three stationary balls, is determined. The greater the wear, the poorer the lubricity of the oil composition. The results of the test are shown in Table I.

From Table I it is seen that at a load of 7.5 kg. the oil composition containing the inventive additive of Example I exhibits only slightly more wear than does the oil composition containing the commercial additive and much less wear than the base hydrocarbon oil containing no additive. Under a load of 40 kg. the oil composition of this invention exhibits less wear than does the oil composition containing the commercially available additive. It is apparent that the degree of lubricity of the oil com position containing the inventive additive is as good as or better than the lubricating oil composition containing the commercial additive and far superior to the base oil.

EXAMPLE V The lubricating oil compositions of Example II containing 10 volume percent of the inventive additive of Example I and 10 volume percent of the commercially available additive, as well as the base hydrocarbon oil containing no additive, are subjected to the Four Ball test to determine the sieze point. The apparatus and procedure are similar to those of the Shell Four Ball Wear test described above except greater loads are applied to the rotatable ball. The load at which the balls sieze and the load at which they weld due to frictional heat are determined. The higher the sieze and weld loads, the greater the degree of lubricity of the oil composition. The results of the test are shown in Table II.

TABLE II Additive concentration in the lubricating oil The data show that the oil composition containing the additive of the invention has sieze and weld loads equal to those of the oil composition containing the commercial additive and appreciably greater than those of the base hydrocarbon oil. It is again evident that the additives of this invention increase the lubricity of hydrocarbon lubricating oils in which they are incorporated.

The lubricating oil composition containing the additive of Example I, in addition to having increased detergency and lubricity characteristics as well as rust inhibitory properties, will also exhibit good thermal stability. In addition, engines lubricated with the inventive lubricating oil composition will be characterized by enhanced cleanliness.

The detergency additive of this invention may be prepared by condensing various aliphatic polyamines with various mixtures of monocarboxylic acid and polyhalo aliphatic acid having a terminal -CF group. Suitable additives may be prepared, for example, by condensing any of the following aliphatic polyamines with mixtures of any of the following monocarboxylic acids and polyhalo aliphatic acids wherein the mixed acids comprise about 50 to 99 mole percent, and preferably about 70 to 95 mole percent, of the monocarboxylic acid and about 50 to 1 mol percent, and preferably about 30 to mole percent, of the polyhalo aliphatic acid having a terminal CF group. The condensation product may have about 50 to 100%, and preferably about 60 to 90%, of the amino groups converted to amide groups.

Polyhalo aliphatic Aliphatic polyamine Monocarboxylic acid acld Ethylenediamine fi-methylheptanoic 4,4,4trifiuorobutyiic aci 2-chloro 6, 6, fi-trifluorohexanoic acid. 2, 2-dichloro-4, 5-

dibromo-lO, 10,

am l, 3-propylenediamine Q-ethyldodecanoic act 1,20-diaminocicosane- 18-butyleicosoic acid Lubricating oil compositions containing the detergency additives of this invention may be prepared containing from about 1 to 20% by volume, and preferably about 2 to 10% by volume, of the additive. While the detergency additives of this invention are useful in lubricating oils generally, it is contemplated that their greatest utility will be in 2-cycle engine oils.

While our invention has been illustrated by various specific examples, it will be understood that the scope of our invention is not restricted thereto.

We claim:

1. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and a minor proportion of a detergency additive comprising the condensation product of an aliphatic polyamine and a mixture comprising about 50 mole percent to about 99 mole percent of a monocarboxylic acid containing about 8 to 30 carbons and about 50 mole percent to about 1 mole percent of a polyhalo aliphatic monocarboxylic acid having a terminal CF group and containing about 4 to 24 carbons wherein said mixture of monocarboxylic acids is in the amount of at least about 0.5 mole per equivalent of amino groups in said polyamine whereby at least 50% of the amino groups of the polyamine are converted to amide groups by condensation with said mixture of acids.

2. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 1 to 20% by volume of the detergency additive of claim 1 wherein said aliphatic polyamine contains 2 to about 30 carbons and 2 to about 16 amino groups, and said mixture of monocarboxylic acids is in the amount of about 0.5 to 1 mole per equivalent of amino groups in said polyamine whereby about 50 to 100% of the amino groups of said polyamine are converted to amide groups by condensation with said mixture of acids.

3. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 2 to 10% by volume of the detergency additive of claim 2 wherein the aliphatic polyamine is a polyalkylenepolyamine containing about 3 to 20 carbons and 2 to about 8 amino groups; the monocarboxylic acid is an isoaliphatic acid containing about 12 to 24 carbons; the polyhalo aliphatic monocarboxylic acid containing a terminal CF group is a perfluoroaliphatic monocarboxylic acid containing about 8 to 16 carbons; the mixture of acids comprises about 70 mole percent to about 95 mole percent of said isoaliphatic acid and about 30 mole percent to about 5 mole percent of said perfluoroaliphatic monocarboxylic acid; and said mixture of monocarboxylic acids is in the amount of about 0.6 to 0.9 mole per equivalent of amino groups in said polyalkylenepolyamine whereby about 60 to of the amino groups of the polyalkylenepolyamine are converted to amide groups by condensation with said mixture of acids.

4. A 2-cycle engine oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 2 to 10% by volume of the detergency additive of claim 3 wherein the polyalkylenepolyamine is tetraethylenepentamine; the isoaliphatic acid is isostearic acid; the perfiuoroaliphatic monocarboxylic acid is perfluorooctanoic acid; the mixture of acids comprises about 90 mole percent of isostearic acid and about 10 mole percent of perfluorooctanoic acid; and said mixture of monocarboxyhc acids is in the amount of about 0.6 mole per equivalent of amino groups in said tetraethylenepentamine whereby about 60% of the amino groups of the tetraethylenepentamine are converted to amide groups by condensation with said mixture of acids.

References Cited UNITED STATES PATENTS 2,824,884 2/1958 Barnhart et al. 25251.5 A

3,219,666 11/1965 Norman et al. 25251.5 A

3,298,955 1/1967 Strang 252-515 A 3,310,492 3/1967 Benoit 252-51.5 A

3,444,170 5/1969 Norman et al. 252-515 A FOREIGN PATENTS 529,167 8/1956 Canada 252-515 A DANIEL E. WYMAN, Primary Examiner W. I. SHINE, Assistant Examiner U.S. C1. X.R. 252392, 403 

